Echolocation is practiced by dolphins, bats and other animal species to supplement their vision. They bounce sound vibrations off objects and get a sense of where these objects are based on how the vibrations come back to them.
Daniel Kish taught himself how to use echolocation (or as he refers to it, "FlashSonar" as well. Kish was born with an aggressive cancer that attacked his retinas. In order to save his life, both of his eye balls were removed and replaced with prosthetic ones. Being completely blind, Kish figured out how to supplement his lost vision.
He creates a sharp click with his tongue and listens for how the faint sound vibrations bounce off objects around him. He is able to describe his surroundings in minute details - right down to the bad parking job of his interviewer. He bikes in heavy traffic, camps by himself and is a skilled cook and dancer.
Kish, along with several coworkers, runs a nonprofit called World Access for the Blind. It trains blind people how to better interact with their environment using echolocation. Kish supports full independence for blind people and his skills demonstrate that this is possible.